For many, this game should be fairly intuitive to complete on your own, but some may struggle (as I did) with the time-related achievements. This guide is mainly to tell you exactly how you need to idle for those achievements, plus the others just to make a complete guide.

We can repeat
The game has begun


First of all, just select "New Game" on the main menu. This will trigger this achievement.

Hitler kaput
Complete the game


So for this one, you do not need to actually complete the game, but simply shoot an enemy or two.
In the first room, just go up to the door and it'll slide open upon walking up to it.
There is an enemy in the next room; stab it and the achievement should be yours.*
*I've heard for some that they need to kill more than one enemy for the achievement to pop. If the achievement does not pop upon killing the first enemy, just go to the next room and kill the enemies that are in there.

Nazi breakfast
Spend in the game one minute


To be shot
Spend in the game five minute


War never changes
Spend in the game ten minute


I'll start out by saying that the achievement descriptions are a bit misleading. Basically, after you get the one minute achievement, the timer resets and you need to wait another five minutes. Then, after that one pops, you'll need to wait another ten minutes. In total, that's 16 minutes you'll need to idle. If you screw up the achievements (which I'll get to in a second) you'll need to wait 16 minutes again.
For the time-related achievements, you'll need to meet these criteria (some may not be required, but I would follow all of them just to be safe)
1. Do NOT close out the other window that appears. You may notice upon launching the game that another window called "achievements_for_every_game" appears.











If you close this out, the time-related achievements will not pop.

2. Keep the game idling in game. If you just care about the achievements, this means staying on level 1 for 16 minutes. Menu time will not count.

3. Do not click out of the Cornflakenstein window.

4. Do not press escape (brings you to the main menu again). You'll need to restart the game if you do this.

Basically, just go do something else in the meantime that doesn't involve usage of your PC. Or you could just sit around for 16 minutes, but that'd be quite boring.

Hope this helped for anyone struggling to get any time-related achievements to pop. If you have anything to add, feel free to comment and I'll do so as soon as I can.